Apple scab first appears as small, olive-colored lesions on the undersides of the leaves. As the fungus spreads, the top sides of the leaves develop lesions, as well, that may become black or mottled with defined edges. Severely infected trees may become defoliated by mid-summer, making the tree vulnerable to other diseases. The fruit develop black or brown scabs or soft areas.
cytosis. [ 1 sÄ«tÅâ²sis] 2  a condition in which there is a greater than normal number of cells in a tissue or organ.
Sometimes cells need to transport large quantities of substances, too much for passive and active transport to cope with in the time available. They use a process called cytosis. Vesicles, small 'bags' made from the cell surface membrane itself, carry material into the cell (endocytosis) or out of the cell (exocytosis).